Method and device for picture encoding and decoding using illumination compensation

Abstract

A method for reconstructing a picture block is disclosed, wherein the block is predicted using local illumination compensation. The parameters of local illumination compensation are determined according to a selection of reconstructed samples located to the left and above of the current block. In the case where some of them are unavailable, they may be replaced using different techniques.

The invention claimed is: 
     
       1. A method for decoding comprising:
 identifying valid and non-valid samples among neighboring reconstructed samples on a left of a current block and among neighboring reconstructed samples on top of the current block; 
 replacing at least one non-valid sample by another valid sample such that a number of valid samples on the left of the current block and a number of valid samples on the top the current block are both larger than or equal to N; 
 determining local illumination compensation parameters from a first set of N valid samples on the left of the current block and a second set of N valid samples on the top of the current block and their corresponding reference samples neighboring a reference block; and 
 reconstructing the current block from a prediction block obtained by applying local illumination compensation with the local illumination compensation parameters on the reference block. 
 
     
     
       2. The method of  claim 1 , wherein the at least one non-valid sample is a sample not usable for determining the local illumination compensation parameters. 
     
     
       3. The method of  claim 1 , wherein the another valid sample is a sample usable for determining the local illumination compensation parameters. 
     
     
       4. The method of  claim 3 , wherein the another valid sample is obtained by interpolating at least two valid samples, wherein the at least two valid samples are valid samples closest to the non-valid sample to be replaced and interpolating is based on distances between the non-valid sample to be replaced and each of the two valid samples. 
     
     
       5. The method of  claim 1 , wherein the another valid sample is obtained from a set of neighboring samples extended beyond a current block size at a top of the current block and/or at a left of the current block. 
     
     
       6. A non-transitory computer readable medium storing instructions which, when executed by one or more processors, cause the one or more processors to carry out the method of  claim 1 . 
     
     
       7. A decoding apparatus comprising one or more processors and at least one memory coupled to the one or more processors, wherein the one or more processors are configured to perform:
 identifying valid and non-valid samples among neighboring reconstructed samples on a left of a current block and among neighboring reconstructed samples on top of the current block; 
 replacing at least one non-valid sample by another valid sample such that a number of valid samples on the left of the current block and a number of valid samples on the top the current block are both larger than or equal to N; 
 determining local illumination compensation parameters from a first set of N valid samples on the left of the current block and a second set of N valid samples on the top of the current block and their corresponding reference samples neighboring a reference block; and 
 reconstructing the current block from a prediction block obtained by applying local illumination compensation with the local illumination compensation parameters on the reference block. 
 
     
     
       8. The apparatus of  claim 7 , wherein the another valid sample is a sample usable for determining the local illumination compensation parameters. 
     
     
       9. The apparatus of  claim 8 , wherein the another valid sample is obtained by interpolating at least two valid samples, wherein the at least two valid samples are valid samples closest to the non-valid sample to be replaced and interpolating is based on distances between the non-valid sample to be replaced and each of the two valid samples. 
     
     
       10. The apparatus of  claim 7 , wherein the at least one non-valid sample is a sample not usable for determining the local illumination compensation parameters. 
     
     
       11. The apparatus of  claim 7 , wherein the another valid sample is obtained from a set of neighboring samples extended beyond a current block size at a top of the current block and/or at a left of the current block. 
     
     
       12. A method for encoding comprising:
 identifying valid and non-valid samples among neighboring reconstructed samples on a left of a current block and among neighboring reconstructed samples on top of the current block; 
 replacing at least one non-valid sample by another valid sample such that a number of valid samples on the left of the current block and a number of valid samples on the top the current block are both larger than or equal to N; 
 determining local illumination compensation parameters from a first set of N valid samples on the left of the current block and a second set of N valid samples on the top of the current block and their corresponding reference samples neighboring a reference block; and 
 encoding the current block from a prediction block obtained by applying local illumination compensation with the local illumination compensation parameters on the reference block. 
 
     
     
       13. The method of  claim 12 , wherein the another valid sample is a sample usable for determining the local illumination compensation parameters. 
     
     
       14. The method of  claim 13 , wherein the another valid sample is obtained by interpolating at least two valid samples, wherein the at least two valid samples are valid samples closest to the non-valid sample to be replaced and interpolating is based on distances between the non-valid sample to be replaced and each of the two valid samples. 
     
     
       15. The method of  claim 12 , wherein the at least one non-valid sample is a sample not usable for determining the local illumination compensation parameters. 
     
     
       16. The method of  claim 12 , wherein the another valid sample is obtained from a set of neighboring samples extended beyond a current block size at a top of the current block and/or at a left of the current block. 
     
     
       17. A non-transitory computer readable medium storing instructions which, when executed by one or more processors, cause the one or more processors to carry out the method of  claim 12 . 
     
     
       18. An encoding apparatus comprising one or more processors and at least one memory coupled to the one or more processors, wherein the one or more processors are configured to perform:
 identifying valid and non-valid samples among neighboring reconstructed samples on a left of a current block and among neighboring reconstructed samples on top of the current block; 
 replacing at least one non-valid sample by another valid sample such that a number of valid samples on the left of the current block and a number of valid samples on the top the current block are both larger than or equal to N; 
 determining local illumination compensation parameters from a first set of N valid samples on the left of the current block and a second set of N valid samples on the top of the current block and their corresponding reference samples neighboring a reference block; and 
 encoding the current block from a prediction block obtained by applying local illumination compensation with the local illumination compensation parameters on the reference block. 
 
     
     
       19. The apparatus of  claim 18 , wherein the another valid sample is a sample usable for determining the local illumination compensation parameters. 
     
     
       20. The apparatus of  claim 19 , wherein the another valid sample is obtained by interpolating at least two valid samples, wherein the at least two valid samples are valid samples closest to the non-valid sample to be replaced and interpolating is based on distances between the non-valid sample to be replaced and each of the two valid samples. 
     
     
       21. The apparatus of  claim 18 , wherein the at least one non-valid sample is a sample not usable for determining the local illumination compensation parameters. 
     
     
       22. The apparatus of  claim 18 , wherein the another valid sample is obtained from a set of neighboring samples extended beyond a current block size at a top of the current block and/or at a left of the current block.